288 HISTOIIY OF 



with a patience almost equalling that of the sitting ben, have at- 

 tended incubation in all its stages. From them, therefore, we 

 have an amazing histoiy of the chicken in the egg, and of its ad- 

 vances into complete formation. 



It would be methodically tedious to describe those parts of 

 the egg which are weU known and obvious ; such as its shell, its 

 white, and its yolk ; but the disposition of these is not so appa- 

 rent. Immediately under the shell lies that common membrane 

 or skin, which lines it on the inside, adhering closely to it every- 

 where, except at the broad end, where a little cavity is left, 

 that is filled with air which increases as the animal within grows 

 larger. Under this membrane are contained two whites, though 

 seeming to us to be only one, each wrapped up in a membrane of 

 its own, one white within the other. In the midst of all is the yolk 

 wrapped up likewise in its own membrane. At each end of this are 

 two ligaments, called chalazcB, which are, as it were, the poles of this 

 microcosm, being white dense substances, made from the mem 

 branes, and serving to keep the white and the yolk in their places. 

 It was the opinion of Mr Derham that they served also for another 

 purpose ; for a line being drawn from one ligament to the other, 

 would not pass directly through the middle of the yoUc, but 

 rather towards one side, and would divide the yolk into two 

 unequal parts, by which means these ligaments serve to keep the 

 smallest side of the yolk always uppermost ; and in this part be 

 supposed the cicatricula, or first speck of life, to reside ; which 

 by being uppermost, and consequently next the hen, would be 

 thus in the warmest situation. But this is rather fanciful than 

 true, the incipient animal being found in all situations, and not 

 particularly influenced by any.' The cicatricula, which is the 

 part where the animal first begins to show signs of life, is not 

 unlike a vetch, or a lentil, lying on one side of the yolk, and 

 within its membrane. All these contribute to the little animal's 

 (Convenience or supj-ori : the outer membranes and ligaments 

 preserve the fluids in their proper places ; the white serves as 

 nourishment, and the yolk, with its membranes, after a time be- 

 comes a part of the animal's body.^ This is a description of a 

 hen's egg, and answers to that of all others how large or how 

 small soever. 



1 Haller. S Ibid. 



